Receiving system



Feb. 1, 1938. B. TREvoR ET AL REGEIYING SYSTEM Filed Feb. 23, 1935 Patented Feb. 1, 19,38

unirsi)N ys'rii'ras RECEIVHNG SYSTEM Bertram Trevor and Ralph Waldo George, Riverhead, N. Y., assignors to Radio Corporation of America, a corporation of DelawareA Application February Z3, 1935, Serial No. 7,803

13 Claims.

The present invention relates to radio receiving systems, and particularly to systems which a re adapted Ato receive ultra short Wave energy.

One of the objects of the present invention is to provide a highly eicient and simple ultra short Wave radio receiver.

Another object is to provide an improved radio frequency tuned oscillatory circuit having low loss.

A further object is to provide a receiver characterized by high frequencystability and capable of receiving signals having wide band modulation.

An important feature of the invention lies in ing the received energy. More speciiically, the oscillatory circuit comprises a low loss, radiationless, concentric arrangement having inner and outer concentric tubes which are coupled together at both of their adjacent ends. In the -O preferred arrangement there is provided, within the inner cylindrical tube, two spaced rods for receiving the collected energy, each rod being surrounded for a portion of its length by a hollow, concentrically arranged, cylindrical metallic element. An adjustable cylindrical ring located between the inner surface of the outer tube and outer surface of the inner tube serves to vvary the constants of the oscillatory circuit. At one end ofthe inner conductor there is provided a lumped capacity in the form of /a drum which couples this end with the outer conductor. The ends of the rods extend into this drum and thus have their potentials varied in accordance with o the variations in potential of thecapacity drum. Another feature lies in the provision of a tuned circuit between the antenna and the concentric low loss oscillatory circuit for givingadded radio frequency selectivity for the purpose of reducing 40 the image response in the receiver.' ln the circuit embodiment hereinafter described, this tuned vcircuit comprises a pair of parallel wires conductively coupled together at one end and ca'- pacitively coupled together at their other end, l) but it is to be understood, of course, that any other type of tuned circuit-such as a condenser, coil combination or another concentric low loss alair may replace the parallel wire tuned circuit.

Other objects and features will be apparent from a. reading of the following detailed description which is accompanied by drawing, wherein:

Fig. 1 shows applicants preferred embodiment of a complete radio receiving systemyand Fig. 1a shows a cross-sectional view of the conthe novel oscillatory circuit employed for resonat-` (Cl. 25d-2m centric, low loss oscillatory arrangement of Fig. 1, along the lines .li-A.

Referring to Fig. l, modulated high frequency energy picked up upon antenna. 2 is fed through transmission line d to the tunable trap circuit 6 having the adjustable tuning condenser 8. The transmission line d is variably connected. `or tapped to the sides lll, l2 of the tuned circuit ,6 at points I6, l5, preferably so chosen that the impedance at points i6, i6 matches the surge impedance of the transmission line 4. The conductors lli, l2 of the tuned circuit 6 are substantially linear and are of low loss conductance as is also the bridging conductor I8 grounded at its midpoint by connection 20. At suitable impedance points 22, 24 on the tuned input'circuit 6, the resonated energy from tuned circuit lv is conductively fed on to metallic rods 26, 28 conductiv-ely connected to the end plate 30 of outerv rods 26, 28. About rod 26 there is concentricallyY placed a metallic tube 34 conductively connected to the metallic end plate 30. Similarly, about rod 28 there is placed concentrically a metallic tube 36 also connected to the end plate 30. About both tubes 36, 36 is a further metallic pipe or y tube 38 which is also in conductive connection with end plate 39. Slidably mounted about the tube 3@ is a doughnut or cylindrical metallic end ring @d which may be provided with ears d protruding through slots in the metallic walls 32, whereby the ring fi may be moved at Will along the tube 3d. Preferably, ring Q0 is in intimate frictional metallic contact with the inner surface of the outer conductor tube 32 and the outer surface of. tube or pipe 33. The exterior of the outer conductor tube 32 is'grounded, as shown.

Fig. la shows a cross sectional view of the low loss concentric tube oscillatory arrangement along the line A-A.

The collected energy after being resonated in pull to the grids ed, 50 of detector tubes 52, 54.-

The combination of tuned circuit 6 coupled with the two rod-like resonators 2E, 28 and condenser i6 gives a band pass eiect characterized by a iiat Atop curve having steep sloping sides. This char- 'acteristic gives an image response very much lower than a single resonant circuit.

At the right hand end of tube 38 there is mounted an innerdrum 58, 68. y The ring 48 is scadjusted that the capacity between the inner drum 58, 68 and thel wall 32 and end plate 62 resonates with the linductance of the pipe 38 between the right-hand surface 64 of ring 48 and the inner drum end 68, at a desired frequency of operation for the local oscillation generator 66 the latter being provided with a suitably tuned plate circuit 68 also tuned to the desired local heterodyne frequency. Because of the low loss nature of the grid circuit of the local oscillation generator 66, its frequency remains substantially constant, and because of the nature of the grid circuit chosen and described, sufliciently high frequencies may be generated by the local oscillation generator 66 1 to suitably beat with waves picked up upon antenna 2, assumed, by way of example, to be of the order of frequency of 91.8 megacycles. For Vernier adjustments of frequency a cylindrical vernier condenser 18 is provided, and for automatic frequency control, which shall be described more fully hereinafter, a further Variable condenser 12 is provided.

llength of 38, the capacity of Vernier 18 and the capacity of vernier 12. In one embodiment successfully used, the capacity between drum 68, 58 and 62, 32 was approximately .0002 microfarad for a frequency of 80.3 megacycles.

It is preferred to have the side 64 of the doughnut ring 48 as near the side 68 as possible, in order i to obtain a low L/C ratio, whereby the tuned impedance of the oscillatory circuit 64, 38, 68, 32

across point 84 and the cathode of local oscillator 66 is made asllow,I as possible consistent with obtainable values of capacity between drum 68, 58

and 62, 32, so that the losses presented to the oscillatory circuit' 64, 38, 68, 32 by the grid of local oscillator 66 will be as small as possible. In other words, it is desired to obtain as high a reciprocal of power factor (low loss) in the oscillatory circuit 64, 38, 68,32 as possible, notwithstanding the loading imposed by the grid of local oscillator 66.

t should be noted that there is a smaller reciprocal of power .factor on rods 26, 28 due to their smaller diameter than that of the oscillatory circuit 64, 38, 68. 32. Rods 26, 28 are purposely made longer than the length 38 locatedbetwleen sides 64 and 68 in order to build up an impedance ashigh as possible consistent with the resistance loading imposed by the grids 48, 58 of detectors 52, 54. At the desired dimensions, the resistance loading imposed by the grids 48, 58 will approxil mately match the impedance of rods 26, 28.

Electrically, oscillatory circuit 64, 38, 68, 32 is equivalent to the well known concentric, radiationless, low -loss tuned circuit comprising inner.

and outer conductors conductively coupled together at one of their adjacent ends and capacitively coupled together at their other adjacent ends. For a more complete description of such an arrangement, reference is made to Reissue Patent No. 20,189, granted December 1, 1936, to

` Hans Otto Roosenstein, and to the application of Browder J. Thompson, Serial No. 746,124, led

September 29, 1934.

Sides 58 and 68 of the'capacity drum have practically the same potential with respect to each 'other although the potential of the drum 58, 68

as a whole'varies periodically at the frequency of local oscillator 66 with respect to ground or the outside wall 32. Consequently, that portion of thesignal input circuit comprising rods 26, 28, which is within the drum 58, 68-will also vary periodically at the frequency of the local oscillator 66. It will thus be seen that the locally generated waves of oscillator 66 are fed to the grids 48, 58 cophasally or in push-push fashion, whereas the collected signal waves on rods 26, 28 are fed to these same grids 48, 58 in push-pull. In other words, there are two frequencies on rods 26, 28 which are supplied to the grids 48, 58 in different senses.

A tuned circuit 141s provided for the output of the detector tubes 52, 54 and may be tuned, for example, to 11.5 megacycles when the local oscillation generator 66 is suitably tuned to produce such a beat with the 91.8 megacycle incoming wave picked up on the antenna 2. All the higher frequencies, such as the high beat frequency which is the sum of the two frequencies supplied to detectors 52, 54, the original signal frequency, and any oscillatory frequency due to unbalance'in the plate circuit of the detectors are attenuated and 'thus prevented from entering the circuit 14 by means of choke coils 16, 18

aided by the by-passing effect of condensers 88, 82 so chosen in value as to offer relatively high impedance to the desired beat frequency energy 'appearing in circuit 14. Conversely, inductors 16, 18 offer a low impedance to the desired beat frequency, which is produced by plate rectification, but relatively high impedance to the higher beat produced during the heterodyning process. The entire outer surface 38, 32, 62 of the outer drum is-at rground radio frequency potential and hence the cathode by-passing condensers may be connected directly thereto as shown in the drawing. The grid of the local oscillator 66 is connected to a point 84 on the inner drum surface \58, generation taking place by virtue of feedback through the interelectrode capacity of the tube 66 which will be found amply high for the wave lengths involved.

The inductance of the beat frequency output circuit 14 is formed by two coils 88, 98 effectively connected together for highfrequency currents by condenser 92 and veffectively grounded at that connection point through the. intermediary of condensers '94. symmetrically coupled to the coils 88, 98 is the coil 96 connected to transmission line 98 feeding the beat frequency energy into an intermediate vfrequency band amplifier |88. The output of amplifier |88 is fed into a further detector |82 supplied with local oscillatory energy from a suitable generator |84 and the lower beat output is suitably picked o and amplified in an amplifier |86.. The mean frequency of the energy in amplifier |86 may be, for

example, 460 kilocycles. The output ofA the amplifier |86 may then be fed into the succeeding amplifiers and detector equipment |81, from which the energy is supplied to asuitable recorder. such as a pair of headphones |88.

For automatically controlling the beat frequency of the oscillations obtained by beating the local oscillatory output with the oscillations obtained from the oscillatory circuit 26, 28, 46, a portion of the energy from detector |81 is supplied to frequency control apparatus |89, which is responsive to frequencies either side of the mean or beat frequency to supply a potential current either to lead |||l or so as to enern gize one of the coils |I2 or H3, depending upon whether the frequency of the oscillations is to be increased or decreased, whereby armature lili. connected to continuously rotating telechron motor I I5, is moved to the right or to the left.

Apparatus |09 may be of any type known in the art and preferably comprises relay equipment in thev nature of a dierential solenoid HG and an electromagnetic device in the output of two electron discharge tubes ill, llt, whereby an increase in current through one tube will result in an increase in current through the upper portion of the solenoid and a decrease through the lower portion, or vice versa, causing the armature I I9 to be moved upwardly or downwardly, as the case may be. I'

'I'he movement of rotating armature IM to its right position, for example, in response to the energization of coil H2, will cause the upper portion of IIC to engage' with the inner circular' ring |20 of concentric cam |2|, thus causing cam I2| to rotate in one direction. If rotatinglarmature ||4 is attracted to the left by the energize.- tion of coll H3, then the upper portion of Hd will engage circular ring |22 and cause concentric cam |2I to rotate in the opposite direction to that caused Awhen armature H4 engages ring |20. Since cam |26 is linked to variable condenser l2 by meansvof gears |23, |26, which are mounted on shafts |25, |2, respectively, it will be appreciated that condenser 12 will be automatically 'varied in a direction to compensate for frequency changes in response to variations in the beat frequency. Any change in position of condenser 12 will vary the capacity to ground between l2 and wall 60.

To assist the operator, there is provided a high-low frequency indicator |21 comprising a red lamp and a green lamp to indicate which way frequency compensation-is being made by the automatic frequency control apparatus its. A pair of electromagnetic relays |28, 29 are conductively connected at one cf their ends to leads H0, lli respectively, and at their other ends to ground, whereby the application of potential to one of the leads il!! or til will cause the energization of the associated relay |28 or 29 respectively to light the properl lamp over an obvious circuit.

Although the concentric tuned oscillatory circuit has been described with particular refer-I ence to an input stage. it is to be distinctly under-- stood that the invention is not limited in this respect since the oscillatory circuit may also be used as an output coupling stage, if desired; such a coupling stage may be used between two succeeding electron discharge device circuits. it will thus be evident that various changes may be made in the form, shape and arrangement of the various elements-of the invention to meet condi tions encountered in their use without depart- -ing from the spirit and scope of the appended claims. 1t will also be understood that the concentric tubular inner and outer conductor arrangement is not limited to a conductive coupling at one end since a capacitive coupling at that end would also serve the purpose of the invention..

What is claimed is:

l. The combination with an ultra high frequency oscillatory circuit comprising inner and outer concentric tubular conductors which are coupled together at both'ends, said conductors being capacitively coupled together at least at one end, said capacitive coupling comprising a hollow metallic drum conductively connected to and mounted on said inner tubular conductor, of two spaced conductors within and separated from said inner tubular conductor, said spaced conductors extending into the interior 'of said hollow drum, whereby the potentials of said two spacedl spaced conductors and located within said inner` tubular conductor.

3. The combination with an ultra high frequency oscillatory circuit comprising inner and youter concentric tubular conductors conductively coupled together at one end and capacitively coupled together at their other end, said capacitive coupling comprising a hollow metallic drum electrically connected to and mounted on said inner tubular conductor, of two spaced conductors within and separated from said inner tubular conductors, said spaced conductors extending into the interior of said hollow drum whereby their potentials vary in accordance with variations in potential of said drum, a high frequency input circuit, means coupling said input` circuit, to said spaced `conductors near the ends thereof farthest removed from lsaid hollow drum, an output circuit, and means coupling said output circuit to the other ends of said spaced conductors.

Li. The combination with an ultra high frequency oscillatory circuit comprising inner and outer concentric tubular` conductors conductively coupled together at one end and capacitively coun pled together at their other end, said capacitive coupling comprising a hollow metallic drum electrically connected to and mounted on said inner,

tubular conductor, of two spaced conductors i within and separated from said inner tubular conductors, said spaced conductors extending into the interior of said hollow drum and adapted to have potentials thereon which vary in accordance with variations in potential of saidV drum, a high frequency input circuit, means for adjustably coupling said input circuit to said spaced conductors near the ends thereof which are farthest removedfrorn said hollow drum,an

output circuit in the form ofa pair of electron pacitively coupled together at their other end,

saidcapacitive coupling comprising a hollow metallic drum electrically connected to and mounted on said inner tubular conductor, of two vspaced. conductors within and separated from said inner tubular conductors, said spaced conductors extending into the interior of said hollow drum and adapted to have potentials thereon which vary lin accordance with Variations in-potential of said drum, a high frequency input circuit, means for adjustably coupling said input circuit to said spaced conductors near the ends thereof which are farthest removed from said hollow drum, said input circuit comprising another tuned circuit composed of a pair of parallel wires directly connected together at one end and capacitively coupled together at their other end, and a connec- -tion individual to each of said wires and coupling same to one of said spaced conductors, each connection being'individual to one of said spaced conductors, an output circuit 'in .the form of a pair of electron discharge devices having control grids connected to the other ends of said spaced conductors,I and means for suitably energizing the electrodes of said devices for enabling same to detect the energy on said spaced conductors. y

6. The combination with an ultra high frequency oscillatory circuit comprising inner and outer concentric tubular conductors conductively coupled together at one end and capacitively coupled together at their other end, said capacitive coupling comprising a hollow metallic drum electrically connected to and mounted on said inner tubular conductor, of two spaced conductors within and separated from said inner tubular conductors, said spaced conductors extending into the interior of said hollow drum and adapted ,to have potentials thereon whichvary in accordance with variations in potential of said drum, a high frequency input circuit, means for adjustably coupling said input circuit to said spaced conductors near the ends thereof which are farthest removed from said hollow drum, said input circuit comprising another tuned circuit composed of a pair of parallel wires directly connected together at one end and capacitively coupled together at their `other end, a pair of connections individual to and adjustably movable over each of said wires, each of said pair i of connections comprising one connection coupled to an energy collector and the other connection coupled to one of said spacedconductors, and an output circuit in the form of a pair of electron discharge devices having control grids connected to the vother ends of said spaced conductors, and means for suitably energizing the electrodes of said de'vices for enabling same to detect the energy` on said spaced conductors.

7. A system in`/accordance with claim 6, including a variable condenser connected across said inner conductor to produce corresponding variations on said pair of spaced rods, and anl electron discharge device oscillator having a control electrode coupled to said inner conductor vand a cathode coupled to said'outer conductor.`

9. The combination 'with an ultra high frequency oscillatory circuit comprising concentric inner and outer tubular conductors capacitively coupled together at one end and conductively or capacitively coupled together at their other end, of a pair of spaced conducting rods extending throughout the length of and within said inner tubular conductor, a high frequency input circuit coupled to said rods near one end .thereof and a detector circuit coupled to said rods at or near the vother end thereof, means for enabling variations in potential of said innery conductor to produce corresponding variations on said pair of spaced rods, and an electron discharge device oscillator having a control electrode coupled tov vice'oscillator having tuned input and output.

circuits, said input circuit'comprising a pair of concentric inner and outer hollow tubular conductors capacitively coupled together at one end and electrically lcoupled together at .their other end, a pair4 of spaced conductors extending throughout the length of and located within said inner tubular conductor, means for enabling variations in potential ofl said inner conductor to produce corresponding variations on said last pair of spaced conductors, a condenser connected across one end of said spaced conductors, and means for supplying high frequency energy in push-pull to the other endof said spaced conductors, and a pair of electron discharge devices each having al grid, anode and a cathode, said grids being connected to said spaced conductors whereby energy from said last means issupplied to said grids out of phase and energy from said oscillator is supplied to said grids in phase, and a utilization circuit coupled to said anodes.

1l. In an ultra shot wave heterodyne receiver, means `ifor collecting radiat nergy, a local oscillator, and a detector circuit coupled to said means and said oscillator for producing a beat frequency between said collected energy and the oscillations produced by said local oscillator, the coupling between said detector circuit and said means comprising two pairs of parallel conductors, each pair being directly connected together at one end and capacitively coupled together at their other end, and a connection from each conductor oi one pair of parallel conductors to a conductor of the other pair.

12. A system in accordance with claim 1l, characterized in this, that said connections between the pairs of parallel conductors are adjustably movable over said conductors.

' 13. An ultra high frequency oscillatory circuit between, adjustable means between said inner and said outer conductor for varying said capacitive coupling, and means intermediate the ends of said conductors for. adjustably coupling said conductors together at points along the lengths of said conductors. i

BER'I'RAM 'mnvon l RALPH WALDO GEORGE. 

